M. Posted July 11, 2015 Share Posted July 11, 2015 I was just looking to get the skinny on these eyepieces. Do a lot of you guys run the 2" at lower magnification and then revert back to a 1.25" eyepiece fir the planetary observing? I was thinking about investing in a wide FOV 29mm skywatcher or similar to start with, also will my Hyperion set convert and offer just as good over a dedicated 2" What 2" do you guys find yourself using the most? Link to comment Share on other sites More sharing options...
Tweedledee Posted July 11, 2015 Share Posted July 11, 2015 Yes 2" eps are generally for lower power and wider fields. Higher powers have smaller fields so 1.25" is sufficient. What is the diameter of the opening into your baffle tube. If it is smaller than about 30mm that is likely to cause some vignetting of 2" eyepieces with larger field stops. Ie: the brightness may dim a little towards the edge of the field of view. You use 2" eps to achieve wider fields of view. The maximum eyepiece field stop in a 1.25" ep is about 29mm. In a 2" eyepiece it is about 46mm. With a bigger field stop you can take in a lot more sky. You can still get wide fields in your SCT, but I suspect you may notice a little vignetting from the baffle tube, if it is smaller than the ep field stop. It could cost a bit to get a bigger visual back if required and a 2" diagonal. A cheaper route maybe to use 1.25" eps with an F6.3 focal reducer. M. 1 Link to comment Share on other sites More sharing options...
M. Posted July 11, 2015 Author Share Posted July 11, 2015 Approx internal measurment is 42mm Link to comment Share on other sites More sharing options...
Tweedledee Posted July 11, 2015 Share Posted July 11, 2015 Brilliant, you should get full use from 2" eps if that opening is maintained right through the diagonal and into the eyepiece. Link to comment Share on other sites More sharing options...
Tweedledee Posted July 11, 2015 Share Posted July 11, 2015 If you want to get the widest true FOV possible then you need an ep with a field stop approaching 46mm. These are the specs for an ep to give the widest true FOV possible in your scope of up to 1.3 degrees... 50mm 50 degree apparent FOV = 40x 40mm 68 degree apparent FOV = 50x 30mm 82 degree apparent FOV = 67x 25mm 100 degree apparent FOV = 80x They will all perform well in your SCT, but the 50 degree will be like looking at your smartphone, 82 degree like your 50" TV, and the 100 degree will be your IMAX cinema view Link to comment Share on other sites More sharing options...
M. Posted July 11, 2015 Author Share Posted July 11, 2015 Thanks Pete Link to comment Share on other sites More sharing options...
Werisit Posted July 12, 2015 Share Posted July 12, 2015 I use 2" 50mm and 26mm EP's, and from there down to 4mm are 1 1/4. That's on my 130 which has a fl of 905mm. Link to comment Share on other sites More sharing options...
M. Posted July 12, 2015 Author Share Posted July 12, 2015 I use 2" 50mm and 26mm EP's, and from there down to 4mm are 1 1/4. That's on my 130 which has a fl of 905mm. So, I don't really need a load of 2" eyepieces then? I'd be better just investing in a low mag wide FOV one. How did you find the change from 1.25" ? Link to comment Share on other sites More sharing options...
Doc Posted July 13, 2015 Share Posted July 13, 2015 I have one 2" for wide field, used to have the 28mm Uwan now have the 31mm Nagler and the rest or 1.25" eyepieces. I feel there is no need to have a complete set of 2" unless you bucket loads of money M. 1 Link to comment Share on other sites More sharing options...
M. Posted July 13, 2015 Author Share Posted July 13, 2015 I have one 2" for wide field, used to have the 28mm Uwan now have the 31mm Nagler and the rest or 1.25" eyepieces. I feel there is no need to have a complete set of 2" unless you bucket loads of money I was thinking maybe the skywatcher 29mm, because it was priced well and I could maybe afford it lol Link to comment Share on other sites More sharing options...
Tweedledee Posted July 13, 2015 Share Posted July 13, 2015 If you mean the 2" SW 28mm LET Kellner, it is only 58 degrees with and will barely give you a wider field than the maximum you could get in 1.25". I wouldn't buy a 2" diagonal just for that. Link to comment Share on other sites More sharing options...
M. Posted July 13, 2015 Author Share Posted July 13, 2015 If you mean the 2" SW 28mm LET Kellner, it is only 58 degrees with and will barely give you a wider field than the maximum you could get in 1.25". I wouldn't buy a 2" diagonal just for that. I maybe should rethink then, though I think the price is very attractive against its rivals. Link to comment Share on other sites More sharing options...
Doc Posted July 13, 2015 Share Posted July 13, 2015 I got one of those 28mm Skywatcher LET in the Esprit 120 ED package I bought and have tried it and I didn't enjoy the experience at all. Link to comment Share on other sites More sharing options...
Tweedledee Posted July 13, 2015 Share Posted July 13, 2015 (edited) I got one of those 28mm Skywatcher LET in the Esprit 120 ED package I bought and have tried it and I didn't enjoy the experience at all. I was thinking that we can't really expect much from a £29 ep, especially if it is in a 2" barrel. When I looked at the spec, I was surprised to see it was a modified Kellner. You don't see those very often now. SW know that anyone buying an Esprit is already going to have a case full of top class eps anyway. That or a nice ccd Edited July 13, 2015 by Tweedledee Link to comment Share on other sites More sharing options...
M. Posted July 13, 2015 Author Share Posted July 13, 2015 Well, just scratched that one off the list lol Link to comment Share on other sites More sharing options...
Werisit Posted July 13, 2015 Share Posted July 13, 2015 So, I don't really need a load of 2" eyepieces then? I'd be better just investing in a low mag wide FOV one. How did you find the change from 1.25" ? I really only use the 2" EP's for finding something. Then I change to the 1 1/4"s. It's quite quick and simple to use the 2" to 1 1/4" adapter. That can then stay in the diagonal while the highermag 1 1/4" EP's are changed over. I do get a bit fed up with re-focusing with every change as my EP's are all different makes. Link to comment Share on other sites More sharing options...
Werisit Posted July 13, 2015 Share Posted July 13, 2015 Oh and yes,S-W 28mm LET. I had one with my SW 120ED. I seem to remember there was a little bit in the centre of the view that was fairly sharp, and then, oh dear! Blurry and distorted. My 2" 26mm EP is a "Revalation" that came with my Revalation 10" Dob and it's much better. Link to comment Share on other sites More sharing options...
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